migrate VERSIONING.md to wiki
migrate VERSIONING.md to wiki

xdg/mongo-cxx-driver,mongodb/mongo-cxx-driver,mongodb/mongo-cxx-driver,xdg/mongo-cxx-driver,acmorrow/mongo-cxx-driver,mongodb/mongo-cxx-driver,xdg/mongo-cxx-driver,mongodb/mongo-cxx-driver,acmorrow/mongo-cxx-driver,xdg/mongo-cxx-driver,acmorrow/mongo-cxx-driver,acmorrow/mongo-cxx-driver